Abstract : This paper focuses on the 3D MHD modeling on an arc plasma in a Kvaerner-type torch made of two concentric electrodes. The spots are displaced with an external magnetic field. We observe different phenomenologies in arc movement, ranging from a gliding arc on the electrodes surfaces to jumping arc foot. The former mode induces a lower heat flux at the electrodes surfaces in comparison to the latter. Besides those dynamics which are indebted to gas nature, current and flow rates, arc stability is also investigated with a theoretical model based on an energy principle.